OBJECTIVE Although Essential Tremor is one of the most common movement disorders, we do not currently know which muscles are most responsible for tremor. Determining this requires multiple steps, one of which is characterizing the distribution of tremor among the degrees of freedom (DOF) of the upper limb. METHODS Upper-limb motion was recorded while 22 subjects with ET performed postural and kinetic tasks involving a variety of limb configurations. We calculated the mean distribution of tremor among the seven DOF from the shoulder to the wrist, as well as the effect of limb configuration, repetition, and subject characteristics (sex, tremor onset, duration, and severity) on the distribution. RESULTS On average, kinetic tremor was greatest in forearm pronation-supination and wrist flexion-extension, intermediate in shoulder internal-external rotation and wrist radial-ulnar deviation and then shoulder flexion-extension and elbow flexion-extension, and least in shoulder abduction-adduction. The average distribution of postural tremor was similar except for forearm pronation-supination, which played a smaller role than in kinetic tremor. Limb configuration and subject characteristics did significantly affect tremor, but practically only in forearm pronation-supination and wrist flexion-extension. There were no significant differences between repetitions, indicating that the distribution was consistent over the duration of the experiment. CONCLUSIONS This paper presents a thorough characterization of tremor distribution from the shoulder to the wrist. SIGNIFICANCE Understanding which DOF exhibit the most tremor may lead to more targeted peripheral tremor suppression.

中文翻译：

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特发性震颤患者上肢主要自由度的震颤分布

目标虽然特发性震颤是最常见的运动障碍之一，但我们目前不知道哪些肌肉对震颤负有最大责任。确定这一点需要多个步骤，其中之一是表征上肢自由度 (DOF) 之间的震颤分布。方法 记录上肢运动，同时 22 名 ET 受试者执行涉及各种肢体配置的姿势和运动任务。我们计算了从肩部到手腕的七个 DOF 中震颤的平均分布，以及肢体配置、重复和受试者特征（性别、震颤发作、持续时间和严重程度）对分布的影响。结果 平均而言，前臂旋前旋后和腕屈伸时运动性震颤最大，肩内旋外旋和腕尺桡偏位居中，其次是肩屈伸和肘屈伸，肩外展内收最少。姿势性震颤的平均分布相似，除了前臂旋前-旋后，其作用小于动态震颤。肢体形态和受试者特征确实显着影响震颤，但实际上仅在前臂旋前-旋后和腕屈-伸中。重复之间没有显着差异，表明分布在实验期间是一致的。结论 本文全面描述了从肩部到手腕的震颤分布。